OFFSET
0,6
COMMENTS
Conjecture: (1) The only zero entries are for values of r == 2 (mod 3). (2) There are infinitely many values of k such that 10^k + r is a prime if r is not == 2 (mod 3).
EXAMPLE
The term corresponding to 21 is 3 as 21, 121 both are composite and 1021 is a prime. 1021 = 10^3 + 21 hence k = 3.
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Sep 28 2003
EXTENSIONS
More terms from Ray Chandler, Oct 15 2003
STATUS
approved